Once you have created your tables, you can modify their structure by using the ALTER TABLE command. Add columns, modify the column length, add or drop constraints, and enable or disable constraints by using this command. If you want to remove a table, both the rows and the data structure of a table, invoke the DROP TABLE command. Other commands that affect tables that are covered in this lesson are RENAME, to change a database object name. TRUNCATE, to remove all rows from a table. COMMENT, to add a comment about a database object to the data dictionary. All of these commands are data definition commands. | 12 Altering Tables and Constraints ORACLG Objectives Add and modify columns. Add enable disable or remove constraints. Drop a table. Remove all rows leaving the table definition intact. Change object names. Add comments to objects and view comments from the data dictionary. Timing Schedule 30 minutes 40 minutes 70 minutes Topic Lecture Practice Total Class Management Note Files required for this lesson are Demonstration None Practice None 12-2 Introduction to Oracle SQL and PL SQL Using Procedure Builder Objectives After you create your tables you may need to change the table structures because you omitted a column your column definition needs to be changed or you want to enable or disable constraints. This lesson will demonstrate how you can amend table structures as well as add and remove constraints. At the end of this lesson you should be able to Add and modify table columns. Add enable disable or remove constraints. Drop a table. Remove all rows leaving the table definition intact. Change object names. Add comments to objects and view comments from the data dictionary. Altering Tables and Constraints .
